Eye-tracking systems are available in the related art. Eye-tracking refers to the recording of the eye movements of a person made up primarily of fixations (points which are looked at specifically), saccades (rapid eye movements) and regressions. Devices and systems are referred to as “eye tracker” which carry out this recording and permit an analysis of the eye movements and viewing direction. Modern eye trackers are made of short-range infrared cameras that produce reflections on the retina using a lighting unit. The calibrated positions of pupil and reflections allow a precise identification of the viewing direction of the driver. FIG. 1 shows a schematic model for calibrating such a system. Here, different positions of a pupil with reflections are indicated by A. C indicates a lighting unit for illuminating the pupil. B indicates a camera system for photographing the pupil and the reflections. D represents a visual focus field. In this case, the specific pupil position and reflection are photographed with the camera for different image points on the focus field. Based on this data, the different image points and pupil positions are allocated with the aid of a transfer function E. From this, the correspondingly viewed image points may be determined for future pupil positions.
European Patent Application No. 2 325 722 A describes a method for modulating an operation of a device, including:                Mounting a hardware sensor in or on the device to sense the attentiveness of a user as related to the device;        Processing a signal of the hardware sensor and outputting a coefficient or an index of the attentiveness of the user with regard to the device; and        Adapting the operation of the device on the basis of the coefficient or the index of the attentiveness of the user with respect to the device;        the adaptation being initiated by the device and including an alert and/or information and/or communication to the user based on the attentiveness of the user with respect to the device.        